The volcanic and sedimentary Chatham Islands lie c.800 km east of the South Island of New Zealand (EBA 207) to which they belong politically. The EBA includes the two main islands of Chatham and Pitt, and the much smaller offshore islands of South East (or Rangatira, c.2 km²), Mangere and Star Keys, all of which are important for restricted-range landbirds.

Native vegetation includes coastal broadleaf forest and scrub and shrubland communities, with tall heath forest inland, interspersed with moorland and bogs.

Only five endemic landbirds are today extant on the Chatham Islands: two are birds of the shore and three live in forest, scrub and grassland. One, Thinornis novaeseelandiae, was recorded from the South Island of New Zealand in 1773 but was quickly exterminated after the arrival of European carnivores; its former alleged distribution on the North Island of New Zealand cannot be verified and is in some doubt (Turbott 1990).

Since Polynesian, European and Maori settlement, much of the Chatham Islands' natural vegetation has been cleared by burning and grazing for farming and development, including on the two small islands, South East and Mangere, which are today protected as reserves. This habitat loss, along with hunting, introduced predators and competitors, have all contributed to the destruction of birdlife on the islands, particularly on Chatham and Pitt (less so on South East and Mangere Islands, which are predator-free, cats having died out naturally on Mangere). In total, of 67 bird species and subspecies recorded, 29 became extinct in pre-European times and eight have died out subsequent to European settlement (Atkinson and Bell 1973), including three species since 1800.

All the endemic landbirds are considered threatened or Near Threatened, including three species which have very small populations and which are thus classified as Endangered: Thinornis novaeseelandiae (130 birds in 1993), Haematopus chathamensis (c.100 in 1994) and Petroica traversi (170 in February 1995: D. V. Merton in litt. 1995). This last species became restricted to Little Mangere in the late 1880s and a century later was down to just five birds, including only one viable pair; its recovery represents an amazing conservation success, involving the transfer of the entire remnant population to Mangere and an egg-manipulating, cross-fostering programme (Butler and Merton 1992).

A further four endemic subspecies are also considered priorities for conservation action by Molloy and Davis (1992) and Tisdall (1994): Chatham Island Pigeon Hemiphaga novaeseelandiae chathamensis (may be a full species, c.100 individuals), Forbes's Parakeet Cyanoramphus auriceps forbesi (may also be a full species, c.100: see Triggs and Daugherty 1996); Chatham Island Tomtit Petroica macrocephala chathamensis (c.1,000 birds) and Chatham Island Tui Prosthemadera novaeseelandiae chathamensis (250-350 birds) (B. D. Bell in litt. 1993, 1996).

Threatened seabirds, all of which are endemic breeders, include Magenta Petrel Pterodroma magentae (Critical; 45-150 birds), Chatham Islands Petrel P. axillaris (Critical; c.500), Pitt Shag Phalacrocorax featherstonii (Vulnerable; fewer than 2,000) and Chatham Islands Shag P. onslowi (Vulnerable; fewer than 1,000). Chatham Albatross Diomedea cauta eremita (treated as a full species by Robertson and Nunn in press) is found on Pyramid Rock, where breeding is confined to less than 10 ha, and, although it is fairly numerous (3,200-4,200 pairs) it is suffering from a reduction in the vegetation, probably as a result of climate change.

Conservation programmes are being undertaken for all threatened species and most subspecies. An active programme of reserving and restoring habitat is under way including fencing, controlling herbivores and re-planting, and South East Island has recovered well (B. D. Bell in litt. 1993). Recent information is provided by Holdaway (1994) and the conservation of seabirds is discussed in Bell and Robertson (1994).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Chatham Islands. Downloaded from https://datazone.birdlife.org/eba/factsheet/209 on 23/11/2024.